Image capturing apparatus

ABSTRACT

The light receiving portion of the CCD is divided into three fields. After shooting is finished, the image data of a first field is read out first. Then, when the image data of a second field is read out, AE and WB correction values are calculated based on the image data of the first field. When the image data of a third field is read out, correction is performed based on the calculated AE and WB correction values. Then, the image data of the first and the second fields are processed based on the AE and WB correction values. With this, image processing can be swiftly performed with respect to the AE and WB corrections. Moreover, since image processing is performed not based on information obtained prior to shooting but based on information (image data) obtained at the time of shooting, image processing can be appropriately performed irrespective of changes in shooting condition.

[0001] This application is based on the application No. 2002-158861filed in Japan, the contents of which are hereby incorporated byreference.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] The present invention relates to an image capturing apparatus inwhich the pixel arrangement of the light receiving portion having acolor filter is divided into a plurality of fields each includingcomponents of all the colors of the color filter and charge signalsaccumulated at the time of shooting can be read out field by field.

[0004] 2. Description of the Related Art

[0005] In recent years, the number of pixels of the light receivingportions of digital cameras has been rapidly increasing. On the otherhand, in order that the overall size of the light receiving portion doesnot increase according to the number of pixels, the light receiving areaof the unit light receiving elements (unit CCD cells) is reduced as thepixel density of the light receiving portion increases. Consequently,the image capture sensitivity decreases. To prevent this reduction insensitivity, a technique is known of reducing the area of the chargetransfer path that does not contribute to the photoelectric conversionfunction. However, when the area of the charge transfer path is reduced,it is difficult to parallelly read out the charge signals on all thelines of the light receiving portion at a time. To solve this problem, amethod is adopted such that the light receiving portion is divided intoa plurality of fields and the charge signals of all the pixels aresequentially read out field by field.

[0006] Japanese Laid-Open Patent Applications Nos. 2000-308075 andH10-327354 disclose a method such that with the fragmentation of thefunction of the image sensor, a plurality of fields is read out based ona relationship between TV scanning and the number of pixels.

[0007] As described above, for image capturing apparatuses typified bydigital cameras, the method of dividing the light receiving portion intoa plurality of fields and reading out the image signals of all thepixels field by field (hereinafter, referred to as “field-sequential allpixel readout method”) is adopted from various objects. Further, it isconceivable that a method will expand such that a frame is divided intonot only two or three fields but also a larger number of fields (Nfields where N is a given integer equal to or greater than 2) as thenumber of fields corresponding to one frame and all the pixels are readout.

[0008] In conventional image sensors of a two-field readout type, it isimpossible to read out adjoining pixel lines as image signals of thesame field. Therefore, in the case of color filters adopting the Bayerarrangement, it is impossible to obtain color information of all thecolors only with a first field image or a second field image as shown inFIGS. 12(a), 12(b), 13(a) and 13(b). Consequently, to obtain colorinformation of all the colors for performing AE (automatic exposure)correction and WB (white balance) correction, the following methods arenecessary: (1) Color information of all the colors is obtained prior toactual shooting by use of another readout mode (for example, high-speedreadout mode of thinning out readout lines in the vertical direction asshown in FIG. 14 and obtaining information of all the colors); or (2)after the readout of the image data of all the fields is finished,information of all the colors is obtained from the image data.

[0009] However, according to the all color information obtaining methodsas described above, AE and WB corrections and swift processing inresponse to changes in shooting condition are difficult. That is,according to the obtaining method of (1), since the AE and WB correctionamounts at the time of shooting are determined based on the colorinformation obtained prior to shooting, it is difficult to handleshooting under a flickering light source such as a fluorescent lamp or amercury lamp and a case where the light source condition differs betweenprior to shooting and after shooting such as flash shooting. Accordingto the obtaining method of (2), although changes in shooting conditioncan be handled, in an image capturing apparatus having a high-pixelimage sensor, after all the image data is read out from the imagesensor, color information necessary for AE and WB corrections isobtained and corrections are performed. Therefore, the time fromshooting to the completion of the corrections is long, so thatinstantaneity is impaired. This problem is more significant as thenumber of pixels of the image sensor increases.

SUMMARY OF THE INVENTION

[0010] To solve the above-mentioned problems, an object of the presentinvention is to provide an image capturing apparatus capable ofappropriately and swiftly performing image processing irrespective ofchanges in shooting condition.

[0011] In order to achieve the object, an image capturing apparatusaccording to the present invention comprises: an image sensor in which alight receiving portion having a color filter is provided; a reader fordividing a pixel arrangement of said light receiving portion of saidimage sensor into a plurality of fields, and reading out charge signalsfrom said image sensor field by field; an image processor for performingpredetermined image processing on image data corresponding to the chargesignals read out by said reader; and a calculator for calculating aprocessing parameter used for said predetermined image processing bysaid image processor based on image data corresponding to the chargesignals of a first field from which the charge signals are read outfirst.

[0012] According to the present invention, since processing parametersused for predetermined image processing are calculated based on theimage data corresponding to the charge signals of the first fieldincluding components of all the colors, image processing can beappropriately and swiftly performed irrespective of changes in shootingcondition.

[0013] In the following description, like parts are designated by likereference numbers throughout the several drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0014]FIG. 1 is a perspective view showing an image capturing apparatus1A according to a first embodiment of the present invention;

[0015]FIG. 2 is a rear view of the image capturing apparatus 1A;

[0016]FIG. 3 is a view showing function blocks of the image capturingapparatus 1A;

[0017]FIG. 4 is a view of assistance in explaining the flow of imagesignals in the image capturing apparatus 1A;

[0018] FIGS. 5(a) to 5(c) are views of assistance in explaining a methodof reading out charges from a CCD 2;

[0019]FIG. 6 is a flowchart of assistance in explaining the basicoperation of the image capturing apparatus 1A;

[0020]FIG. 7 is a view of assistance in explaining the operation of theimage capturing apparatus 1A;

[0021]FIG. 8 is a view showing function blocks of an image capturingapparatus 1B according to a second embodiment of the present invention;

[0022]FIG. 9 is a view of assistance in explaining the operation of animage capturing apparatus 1B;

[0023]FIG. 10 is a view of assistance in explaining the flow of imagesignals in an image capturing apparatus 1C according to a thirdembodiment of the present invention;

[0024] FIGS. 11(a) and 11(b) are views of assistance in explaining a CCDcharge readout method according to a modification of the presentinvention;

[0025] FIGS. 12(a) and 12(b) are views of assistance in explaining theCCD charge readout method according to the prior art;

[0026] FIGS. 13(a) and 13(b) are views of assistance in explaining theCCD charge readout method according to the prior art; and

[0027]FIG. 14 is a view of assistance in explaining the high-speedreadout mode of the CCD according to the prior art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0028] <First Embodiment>

[0029] <Structure of Relevant Part of Image Capturing Apparatus>

[0030]FIG. 1 is a perspective view showing an image capturing apparatus1A according to a first embodiment of the present invention. FIG. 2 is arear view of the image capturing apparatus 1A. In FIGS. 1 and 2, threeaxes X, Y and Z orthogonal to one another are shown for clarification ofthe directional relationship.

[0031] A taking lens 11 and a finder window 13 are provided on the frontof the image capturing apparatus 1A. A CCD (charge coupled device) 2 asan image sensor photoelectrically converting subject images incidentthrough the taking lens 11 to thereby generate image signals is providedinside the taking lens 11.

[0032] The taking lens 11 includes a lens system that can be driven inthe direction of the optical axis. The subject image formed on the CCD 2can be brought into in-focus state by driving the lens system in thedirection of the optical system.

[0033] A shutter button 14 and a mode switching button 15 are disposedon the top of the image capturing apparatus 1A. The shutter button 14 isa button which the user depresses to instruct the image capturingapparatus 1A to perform shooting when shooting a subject.

[0034] The mode switching button 15 is a button for switching of modessuch as a shooting mode and a playback mode.

[0035] A slot 16 for inserting a memory card 9 for recording image dataobtained by shooting is formed on a side of the image capturingapparatus 1A. Further, a card extraction button 17 depressed when thememory card 9 is extracted from the slot 16 is disposed. The memory card9 can be extracted from the slot 16 by operating the card extractionbutton 17.

[0036] A liquid crystal display (LCD) 18 for live view display ofdisplaying the subject in the form of a moving image prior to actualshooting and display of shot images is provided on the rear of the imagecapturing apparatus 1A. Moreover, operation buttons 19 for changing thesetting conditions of the image capturing apparatus 1A such as theshutter speed and a finder window 13 are provided on the rear of theimage capturing apparatus 1A.

[0037]FIG. 3 is a view showing function blocks of the image capturingapparatus 1A. FIG. 4 is a view of assistance in explaining the flow ofimage signals in the image capturing apparatus 1A.

[0038] The image capturing apparatus 1A has: an AFE (analog front end) 3connected to the CCD 2 so that data transmission can be performed; animage processing block 4 connected to the AFE 3 so that datatransmission can be performed; and a camera microcomputer 5 performingcentralized control of these elements.

[0039] The CCD 2 has a light receiving portion 2 a on the surfaceopposed to the taking lens 11, and a plurality of pixels is arranged onthe light receiving portion 2 a. The pixel arrangement constituting thelight receiving portion 2 a is divided into three fields, and the chargesignals (image signals) accumulated at the pixels can be sequentiallyread out field by field.

[0040] FIGS. 5(a) to 5(c) are views of assistance in explaining a methodof reading out charges from the CCD 2. In actuality, not less thanseveral millions of pixels are arranged. FIGS. 5(a) to 5(c) show onlypart of them for convenience of illustration.

[0041] A color filter corresponding to the pixel arrangement is providedin the light receiving portion 2 a. This color filter comprisesperiodically distributed red (R), green (Gr, Gb) and blue (B) filters,that is, three kinds of color filters having different colors from oneanother.

[0042] To read out the charge signals accumulated in the cells of theCCD 2, first, as shown in FIG. 5(a), the charge signals in the first,the fourth, the seventh, . . . lines, that is, in the (3n+1)-th lines (nis an integer) are read out in the light receiving portion 2 a toconstitute a first field image 21. Then, as shown in FIG. 5(b), thecharge signals in the second, the fifth, the eighth, . . . lines, thatis, in the (3n+2)-th lines are read out in the light receiving portion 2a to constitute a second field image 22. Lastly, as shown in FIG. 5(c),the charge signals in the third, the sixth, the ninth, . . . lines, thatis, in the 3n-th lines are read out in the light receiving portion 2 ato constitute a third field image 23. By this charge readout method, thefirst to the third fields 21 to 23 each include components of all thecolors of the color filter, that is, pixels of all of R, G and B.

[0043] Reverting to FIGS. 3 and 4, description will be continued.

[0044] The AFE 3 is an LSI (large-scale integrated circuit) having asignal processor 31 and a TG (timing generator) 32 transmitting a timingsignal to the signal processor 31. The TG 32 transmits a CCD drivingsignal to the CCD 2, and a charge signal is output from the CCD 2 insynchronism with the driving signal.

[0045] The signal processor 31 has a CDS (correlated double sampler)311, a PGA (programmable gain amplifier) 312 serving as an amplifier,and an ADC (A/D converter) 313. The output signals of the fields outputfrom the CCD 2 are sampled by the CDS 311 based on a sampling signalfrom the TG 32, and are amplified to desired values by the PGA 312. Theamplification factor of the PGA 312 can be changed by numerical datathrough a serial communication from the camera microcomputer 5. The PGA312 also corrects image signals based on the AE and WB correction valuestransmitted from a selector 46. The analog signals amplified by the PGA312 are converted into digital signals by the ADC 313, and then,transmitted to the image processing block 4.

[0046] The image processing block 4 has an image memory 41; an AE and WBcalculator 42 connected to the image memory 41 so that datacommunication can be performed; an image processor 43; and acompressor/decompressor 45.

[0047] The image memory 41 comprises, for example, a semiconductormemory, and temporarily stores the image data of the fields 21 to 23converted into digital form by the ADC 313. After stored into the imagememory 41, the image data of all the fields is transmitted to the imageprocessor 43 to generate one image of all the pixels. The image data ofthe first field 21 is also transmitted to the AE and WB calculator 42immediately after stored into the image memory 41.

[0048] The AE and WB calculator 42 calculates AE and WB correctionvalues based on the image data of the first field 21 transmitted fromthe image memory 41 (detailed later). The calculated AE and WBcorrection values are transmitted to the selector 46. The selector 46transmits the AE and WB correction values to the signal processor 31 orthe image processor 43 in accordance with the field readout condition ofthe CCD 2.

[0049] The image processor 43 interpolates the image data transmittedfrom the image memory 41 based on the color filter characteristic of theCCD 2. Further, the image processor 43 generates one frame image bysynthesizing the image data of the fields 21 to 23. Moreover, the imageprocessor 43 performs various image processings such as gamma correctionfor obtaining a natural gradation and filtering for performing edgeenhancement and chroma adjustment. Further, the image processor 43performs AE and WE corrections for adjusting the brightness and thecolor balance of the image data based on the AE and WE correction valuestransmitted from the selector 46.

[0050] A display 44 has the LCD 18, and performs image display based onthe image data obtained by the CCD 2.

[0051] The compressor/decompressor 45 compresses the image dataprocessed by the image processor 43, for example by the JPEG method, andstores it onto the memory card 9 which is a recording medium. Moreover,the compressor/decompressor 45 decompresses the image data stored on thememory card 9 for playback display by the display 44.

[0052] Moreover, the image capturing apparatus 1A has a lens driver 61,a shutter controller 62, a photometer 63, an operation portion 64 and apower source 65 connected to the camera microcomputer 5, respectively.

[0053] The lens driver 61 is for changing the position of the takinglens 11. Automatic focusing and zooming can be performed by the lensdriver 61.

[0054] The shutter controller 62 is a part for opening and closing amechanical shutter (hereinafter, referred to simply as “shutter”) 12.

[0055] The photometer 63 has a photometric sensor, and performs meteringassociated with the subject.

[0056] The operation portion 64 comprises various kinds of operationmembers such as the shutter button 14, the mode switching button 15 andthe operation buttons 19.

[0057] The power source 65 has a battery, and supplies power to theparts of the image capturing apparatus 1A.

[0058] The camera microcomputer 5 has a CPU and a memory, and performscentralized control of the parts of the image capturing apparatus 1A.

[0059] <Processing of the AE and WB Calculator 42>

[0060] The AE and WB calculator 42 calculates an AE correction value(brightness correction value) and WB correction values as imageprocessing parameters based on the image data of the first field 21transmitted from the image memory 41 as described above. The calculationmethod will be described below.

[0061] 1. Method of Calculating WB Correcting Values

[0062] First, a weighted average of each pixel data of the first field21 is obtained by the following expression (1): $\begin{matrix}{\left( {{\overset{\_}{R}}_{wb},{\overset{\_}{G}r_{wb}},{\overset{\_}{G}b_{wb}},{\overset{\_}{B}}_{wb}} \right) = \left( {\frac{\sum\limits_{v}{\sum\limits_{h}{K_{vh}R_{vh}}}}{v \times h},\frac{\sum\limits_{v}{\sum\limits_{h}{K_{vh}{Cr}_{vh}}}}{v \times h},\frac{\sum\limits_{v}{\sum\limits_{h}{K_{vh}{Gb}_{vh}}}}{v \times h},\frac{\sum\limits_{v}{\sum\limits_{h}{K_{vh}B_{vh}}}}{v \times h}} \right)} & (1)\end{matrix}$

[0063] Here, the subscripts v and h represent the numbers of pixels, inthe horizontal and the vertical directions, of the first field 21. Thecoefficient k is a coefficient for adjusting the light ray conditionsuch as frontlight, backlight and the color bias condition. Thecoefficient k can be changed according to the condition. It ispreferable that the weighted average calculation be performed not basedon all the pixels of the first field 21 but based on data of pixelsthinned out in a predetermined distribution to reduce the calculationamount.

[0064] Then, WB correction values gr and gb are calculated by thefollowing expression (2) based on the weighted averages of the pixels ofR, Gr, Gb and B calculated by the expression (1): $\begin{matrix}{\left( {{g\quad r},{g\quad b}} \right) = \left( {\frac{{\overset{\_}{G}r_{wb}} + {\overset{\_}{G}b_{wb}}}{2{\overset{\_}{R}}_{wb}},\frac{{\overset{\_}{G}r_{wb}} + {\overset{\_}{G}b_{wb}}}{2{\overset{\_}{B}}_{wb}}} \right)} & (2)\end{matrix}$

[0065] While a calculation method for the CCD 2 having a primary colorfilter is described above, in the case of a complementary color filter,the WB correction values are calculated by converting pixel outputs ofG, Mg, Ye and Cy into R, Gr, Gb and B data and applying the expressions(1) and (2).

[0066] 2. Method of Calculating AE Correction Value

[0067] First, like the above-described calculation of the WB correctionvalues, a weighted average of each pixel of the first field 21 isobtained by the expression (3) shown below. In this case, a coefficientm different from the coefficient k of the expression (1) is used, andthe pixel outputs of R and B are multiplied by the WB correction valuesgr and gb previously calculated by the expression (2). $\begin{matrix}{\left( {{\overset{\_}{R}}_{ae},{\overset{\_}{G}r_{ae}},{\overset{\_}{G}b_{ae}},{\overset{\_}{B}}_{ae}} \right) = \left( {{g\quad r\frac{\sum\limits_{v}{\sum\limits_{h}{m_{vh}R_{vh}}}}{v \times h}},\frac{\sum\limits_{v}{\sum\limits_{h}{m_{vh}{Cr}_{vh}}}}{v \times h},\frac{\sum\limits_{v}{\sum\limits_{h}{m_{vh}{Gb}_{vh}}}}{v \times h},{g\quad b\frac{\sum\limits_{v}{\sum\limits_{h}{m_{vh}B_{vh}}}}{v \times h}}} \right)} & (3)\end{matrix}$

[0068] Next, a brightness signal component Y is obtained by thefollowing expression (4) based on the weighted averages obtained by theexpression (3): $\begin{matrix}{Y = {{0.299{\overset{\_}{R}}_{a\quad e}} + {0.587\left( \frac{{\overset{\_}{G}\quad r_{ae}} + {\overset{\_}{G}b_{ae}}}{2} \right)} + {0.114{\overset{\_}{B}}_{ae}}}} & (4)\end{matrix}$

[0069] When the reference brightness level is set to Y0, an AEcorrection value α can be calculated by the following expression (5):$\begin{matrix}{\alpha = \frac{Y_{0}}{Y}} & (5)\end{matrix}$

[0070] In the case of a CCD having a complementary filter, thebrightness signal component Y is obtained by the average of the pixeloutputs of G, Mg, Ye and Cy.

[0071] <Operation of the Image Capturing Apparatus 1A>

[0072]FIG. 6 is a flowchart of assistance in explaining the basicoperation of the image capturing apparatus 1A. This operation isperformed by the camera microcomputer 5. FIG. 7 which is a view ofassistance in explaining the operation of the image capturing apparatus1A is a timing chart showing a vertical synchronizing signal VD, theshutter 11, the output of the CCD 2 and the image processing. Theflowchart of FIG. 6 will be described with reference to FIG. 7.

[0073] First, live view shooting is performed with the shutter 12opened, and the live view image obtained by the CCD2 is displayed on thedisplay 44. Then, when the shutter button 14 is depressed by the user,shooting is performed (step S1).

[0074] When shooting is finished, the image data of the first field 21accumulated in the CCD 2 is read out with the shutter 12 closed (stepS2).

[0075] At step S3, the image data of the first field 21 read out at stepS2 is stored into the image memory 41.

[0076] At step S4, it is determined whether the readout of the imagedata of the first field 21 is completed or not. When the readout iscompleted, the process proceeds to step 5 and step 10. When the readoutis not completed, the process returns to step S2.

[0077] At step S5, the image data of the first field 21 stored into theimage memory 41 at step S3 is read out. As shown in FIG. 7, a readoutoperation Tr is performed from the completion of the readout of theimage data of the first field 21.

[0078] At step S6, the display 44 performs image display based on theimage data of the first field 21 read out at step S5. With this, theshot image can be swiftly displayed.

[0079] At step S7, the AE and WB calculator 42 calculates the AE and WBcorrection values based on the image data of the first field 21 read outat step S5. As shown in FIG. 7, a calculation processing Tc is performedimmediately after the completion of the readout operation Tr. Thecalculation processing Tc is performed in parallel with the readout ofthe second field 22 from the CCD 2. By thus performing parallelprocessing, the correction at step S13 described later can be performedwithout any trouble by a calculation capability of the AE and WEcalculator 42 that can complete the calculation by the time the readoutof the second field 22 is completed.

[0080] At step S8, the field number ir of the field from which chargesare being read out at the time of completion of the calculationprocessing Tc is detected. In the case of FIG. 7, the field number ir ofthe field from which charges are being read out is 2.

[0081] At step S9, the AE and WB correction values calculated at step S7are set to the PGA 312. As shown in FIG. 7, a setting operation Ts1 isperformed immediately after the completion of the calculation of the AEand WB correction values. With this, the image data of the fieldsubsequent to the field of the field number ir detected at step S8 canbe corrected by the PGA 312.

[0082] At step S10, 2 is assigned to a variable i.

[0083] At step S11, the image data of the i-th field is read out fromthe CCD 2.

[0084] At step S12, it is determined whether the variable i is higherthan the field number ir detected at step S8 or not. When i>ir, theprocess proceeds to step S13. When i≦ir, the process proceeds to stepS14. When i≦ir, unlike step S13, correction based on default values isperformed by the PGA 312.

[0085] At step S13, the PGA 312 performs correction based on the AE andWB correction values set at step S9. In the case of FIG. 7, the imagedata of the third field 23 read out after the setting operation Ts1 iscorrected. That is, the PGA 312 performs image processing on the imagedata of a predetermined field (third field) of the fields other than thefirst field. With this, the AE and WB corrections on the shot image canbe started earlier, so that the correction is completed earlier, thatis, image processing can be swiftly performed.

[0086] At step S14, the image data of the i-th field is stored into theimage memory 41.

[0087] At step S15, it is determined whether the readout of the imagedata of the i-th field is completed or not. When the readout iscompleted, the process proceeds to step S16. When the readout is notcompleted, the process returns to step S11.

[0088] At step S16, it is determined whether the variable i is higherthan the field number ir detected at step S8 or not. When i>ir, theprocess proceeds to step S17. When i≦ir, the process proceeds to stepS18.

[0089] At step S17, the display 44 performs image display based on theimage data of the ir-th field read out at step S11. Specifically,instead of the image of the first field 21 displayed at step S6, theimage of the third field 23 is displayed. With this, the image datahaving undergone the AE and WB corrections by the PGA 312 can be swiftlydisplayed on the display 44.

[0090] At step S18, i+1 is assigned to the variable i.

[0091] At step S19, it is determined whether the variable i is higherthan 3 or not. When i>3, the process proceeds to step S20. When i≦3, theprocess returns to step S11.

[0092] At step S20, the AE and WB correction values calculated at stepS7 is set to the image processor 43. As shown in FIG. 7, an AE and WBcorrection value setting operation Ts2 is performed prior to an imageprocessing Tg performed at step S21.

[0093] At step 21, the image data is read out from the image memory 41,and image processing is performed by the image processor 43. AE and WBcorrections on the image data of a field subsequent to the (ir+1)-thfield, that is, the third field 23 has been performed at step S13.Therefore, at step S21, correction based on the AE and WB correctionvalues set at step S20 is performed on the image data of the otherfields, that is, the first and the second fields 21 and 22. That is, theimage processor 43 performs image processing on the image data of theremaining fields (the first and the second fields) other than the thirdfield.

[0094] When the operation at step S21 is finished, the image data havingundergone the image processing is displayed on the display 44, and isstored onto the memory card 9.

[0095] By the above-described operation of the image capturing apparatus1A, the image data of the third field before stored into the imagememory is corrected based on the AE and WB correction values calculatedfrom the image data of the first field, so that image processing isswiftly performed. Moreover, since correction is performed based on theimage data obtained at the time of shooting, image processing can beappropriately performed irrespective of changes in shooting conditionsuch as a flicker of a fluorescent lamp.

[0096] <Second Embodiment>

[0097]FIG. 8 is a view showing function blocks of an image capturingapparatus 1B according to a second embodiment of the present invention.

[0098] The image capturing apparatus 1B is structured as an imagecapturing apparatus of a type having an optical reflex viewfinder(hereinafter, referred to as “SLR type”). That is, a mirror 66, afocusing screen 67 and a prism 68 are added to the image capturingapparatus 1A of the first embodiment shown in FIG. 3. The imagecapturing apparatus 1B also has a flash 69.

[0099] In FIG. 8, the same function blocks as those of the firstembodiment are denoted by the same reference numbers and descriptionsthereof are omitted.

[0100] The mirror 66 is in a regular position inclined 45 degrees to theoptical axis as shown in FIG. 8 until the shutter button 14 is fullydepressed by the user, and directs the light image from the taking lens11 toward the focusing screen 67. That is, the mirror 66, the focusingscreen 67 and the prism 68 constitute an optical viewfinder. In thevicinity of the prism 68, a photometric portion 63 is provided.

[0101] When the shutter button 14 is fully depressed by the user, themirror 66 is pivoted upward to a substantially horizontal position, sothat the optical path from the taking lens 11 is opened.

[0102] A program for performing the operation described below is storedin the camera microcomputer 5 of the image capturing apparatus 1B.

[0103] <Operation of the Image Capturing Apparatus 1B>

[0104] The operation of the image capturing apparatus 1B described belowis the operation performed at the time of flash shooting using the flash69. Although similar to the operation of the image capturing apparatus1A of the first embodiment shown in the flowchart of FIG. 6, thisoperation is different therefrom in the shooting operation at step S1.This shooting operation will be described with reference to the timingchart of FIG. 9.

[0105] In the shooting operation of the image capturing apparatus 1B,when the shutter button 14 is fully depressed by the user, a lightemission operation GF by the flash 69 is performed to perform flashshooting.

[0106] In the image capturing apparatus 1B, before the shutter button 14is fully depressed, the mirror 6 is in the regular position shown inFIG. 8 and no subject image can be obtained by the CCD 2, so that theshutter 12 is closed and no live view display is performed.

[0107] In the conventional SLR-type image capturing apparatuses, nooptical image of the subject is formed on the CCD 2 before shooting, andthe AE and WB correction values used for shooting cannot be predicted.Therefore, after the data of all the pixels is read out from the CCD 2and stored into the image memory, the AE and WB correction values arecalculated based on the image data, so that it is impossible to swiftlyperform processing. On the contrary, in the image capturing apparatus 1Bof the present embodiment, as shown in FIG. 9, the AE and WB correctionvalues are calculated based on the image of the first field 21 whilecharges of the CCD 2 are being read out, and are used for the correctionprocessing of the third field 23, so that processing can be swiftlyperformed.

[0108] Moreover, in the conventional image capturing apparatuses, sinceit is difficult to determine the condition of mixed light in flashshooting, there are cases where correction cannot be appropriatelyperformed by the signal processor 31. On the contrary, in the imagecapturing apparatus 1B of the present embodiment, since the contents ofthe correction by the signal processor 31 can be changed in accordancewith the image data (image data of the first field) obtained at the timeof shooting, image processing can be appropriately performed.

[0109] <Third Embodiment>

[0110]FIG. 10 is a view of assistance in explaining the flow of imagesignals in an image capturing apparatus 1C according to a thirdembodiment of the present invention.

[0111] Although having a similar structure to that of the imagecapturing apparatus 1A of the first embodiment shown in FIG. 4, theimage capturing apparatus 1C is different therefrom in that an imagepreprocessor 47 is added instead of the PGA 312 shown in FIG. 4.

[0112] The image preprocessor 47, like the PGA 312, corrects the imagedata of the fields based on the AE and WB correction values calculatedby the AE and WE calculator 42 and transmitted from the selector 46.While analog signals are corrected by the PGA 312, in the imagepreprocessor 47, digital signals transmitted from the ADC 313 arecorrected.

[0113] The operation of the image capturing apparatus 1C is similar tothat of the image capturing apparatus 1A of the first embodiment shownin the flowchart of FIG. 6. However, in the present embodiment, at stepS9 of FIG. 6, the AE and WB correction values are set to the imagepreprocessor 47. Moreover, at step S13, correction by the imagepreprocessor 47 is performed based on the set AE and WB correctionvalues.

[0114] With the above-described operation of the image capturingapparatus 1C, like the first embodiment, image processing can beappropriately and swiftly performed irrespective of changes in shootingcondition.

[0115] The structure of the image capturing apparatus 1C may be appliedto the image capturing apparatus 1B of the second embodiment.

[0116] <Modification>

[0117] The CCD (image sensor) of the above-described embodiments is notnecessarily of a type having three fields, but may be of a type havingtwo fields or four or more fields. For example, in the case of a typehaving two fields, an image sensor adopting the CCD charge readoutmethod shown in FIGS. 11(a) and 11(b) is used. In this image sensor, afirst field image having components of all the colors can be obtained bythe readout shown in FIG. 11(a), and a second field image havingcomponents of all the colors can be obtained by the readout shown inFIG. 11(b).

[0118] According to the present invention, since the number of fieldsthat can be AE-and-WB-corrected in the stage of preprocessing before theimage data is stored into the image memory increases as the number offield divisions increases, image processing can be more swiftlyperformed. When the calculation capability of the AE and WB calculatoris high, since the number of fields that can be image-processed in thestage of preprocessing increases, image processing can also be swiftlyperformed.

[0119] In the calculation of the AE and WB correction values in theabove-described embodiments, it is not essential that the coefficient k(see the expression (1)) and the coefficient m (see the expression (2))in the calculation of the weighted averages be different from eachother, but they may be the same.

[0120] In the above-described embodiments, the AE and WB correctionvalues are calculated in parallel with the readout of the image data ofthe second field. However, the present invention is not limited thereto.It may be performed to calculate the correction values after or duringthe readout of the image data of the first field and read out the imagedata of the second field while correcting it after the calculation ofthe correction values.

[0121] Although the present invention has been fully described by way ofexamples with referene to the accompanying drawings, it is to be notedthat various change and modifications will be apparent to those skilledin the art. Therefore, unless otherwise such changes and modificationsdepart from the scope of the present invention, they should be construedas being including therein.

What is claimed is:
 1. An image capturing apparatus comprising: an image sensor in which a light receiving portion having a color filter is provided; a reader for dividing a pixel arrangement of said light receiving portion of said image sensor into a plurality of fields, and for reading out charge signals from said image sensor field by field; an image processor for performing predetermined image processing on image data corresponding to the charge signals read out by said reader; and a calculator for calculating a processing parameter used for said predetermined image processing by said image processor based on image data corresponding to the charge signals of a first field from which the charge signals are read out first.
 2. An image capturing apparatus according to claim 1, wherein said charge signals of each field include components of all the colors of said color filter, respectively.
 3. An image capturing apparatus according to claim 1, further comprises a memory for storing said image data, and before image data corresponding to the charge signals of a predetermined field other than said first field is stored into the memory, said image processor performs image processing based on said processing parameter on said image data of said predetermined field.
 4. An image capturing apparatus according to claim 3, wherein said calculator calculates the processing parameter in parallel with the read out of charge signals of a second field by said reader, and said image processor performs image processing based on said processing parameter on image data corresponding to the charge signals of a third field.
 5. An image capturing apparatus according to claim 4, wherein after image data corresponding to the charge signals of said first and second field are stored into the memory, said image processor further performs image processing based on the processing parameter on said image data of said first and second field.
 6. An image capturing apparatus according to claim 1, wherein said processing parameter is a brightness correction value of the image data.
 7. An image capturing apparatus according to claim 1, wherein said processing parameter is a white balance correction value of the image data.
 8. An image capturing apparatus according to claim 1, wherein said image data corresponding to the charge signals is analog signals, and said image processor performs said predetermined image processing on said analog signals.
 9. An image capturing apparatus according to claim 1, wherein said image data corresponding to the charge signals is digital signals, and said image processor performs said predetermined image processing on said digital signals.
 10. An image capturing apparatus according to claim 1, further comprises a flash for illuminating a subject, and said image processor and said calculator operate at the time of flash shooting.
 11. An image capturing apparatus according to claim 1, further comprising: a display for displaying an image based on the image data; and a display controller for displaying on said display an image based on the image data corresponding to the charge signals of the first field read out by the reader.
 12. An image capturing apparatus according to claim 11, wherein said display controller further displays on said display an image based on processed image data by said image processor.
 13. A method of image processing of image capturing apparatus comprising the steps of: generating charge signals by an image sensor in which a light receiving portion having a color filter is provided; dividing a pixel arrangement of said light receiving portion of said image sensor into a plurality of fields; reading out charge signals from said image sensor field by field; calculating a processing parameter used for a predetermined image processing based on image data corresponding to the charge signals of a first field from which the charge signals are read out first; and performing said predetermined image processing based on said processing parameter on image data corresponding to the charge signals read out. 